Such a hands-free access system, known to the person skilled in the art, makes it possible to detect the presence of an object such as a hand of a user of the motor vehicle when he approaches a panel handle with a view to opening the panel. Detection of the approach of the hand of a user causes a central unit of the vehicle to order the launching of a hands-free interrogation destined for an identifier carried by the user. If, subsequent to this detection, an authorized identifier responds to this interrogation, the central unit of the vehicle orders the unlocking of the vehicle. For this purpose, the hands-free system uses a detection member placed in the panel handle which measures the signal representative of a hand that approaches the handle to a certain distance. In order to avoid launching untimely interrogations, it is necessary to define a sensitivity level for the hands-free system, that is to say that the system will undertake the hands-free interrogation only if the detection member detects a signal exceeding a threshold value corresponding to the presence of a user's hand at a predetermined maximum distance.
The adjusting of this sensitivity must take two main factors into account. The first element consists in taking into account only detections corresponding to the approaching of a hand sufficiently close to the handle. It is thus possible to thus avoid untimely interrogations of the hands-free system for events not corresponding an intention to access the vehicle.
Nonetheless, if the sensitivity is adjusted to too high a level, that is to say corresponding to a threshold value in relation to a distance close to contact between the hand and the handle, the hands-free system will not have time to carry out the entire hands-free interrogation sequence and unlock the panel when the user pulls the handle. Consequently, the panel will not be able to open. This is what is commonly called the wall effect.
In this context, the present invention is aimed at solving the drawbacks previously mentioned and in particular to propose a hands-free system which adapts to situations so as to make it possible to limit at one and the same time the wall effect while economizing the energy resources of vehicles by limiting untimely interrogations.